The present invention relates to a method for thermally reforming a heavy fuel oil/water emulsion, and more particularly to a method for removing water, an alkali or alkaline earth metal salt and the like contained in said emulsion.
Further, the present invention relates to a method for a thermal reforming method wherein water and a magnesium component are removed from an oil-in-water type emulsion of ORINOCO BITUMEN (trademark: ORIMULSION; hereinafter referred to as "ORIMULSION"), a kind of natural asphalt, to recover a tar component.
A naturally occurring asphalt, which is an ultra-heavy fuel oil produced in the northern part of the Orinoco basin belonging to Venezuela in South America (hereinafter referred to as "ORINOCO BITUMEN"), has been confirmed to be very abundant in reserves, so that the use of ORINOCO BITUMEN in industrial applications such as fuels are expected. Since, however, ORINOCO BITUMEN is solid at room temperature (although it is transportable at 150.degree. C. because the viscosity is lowered to 40 cSt), the handleability is poor.
For this reason, The Venezuela Petroleum Corporation has put ORINOCO BITUMEN, on the market, as an oil-in-water type emulsion (ORIMULSION) for use as a fuel for boilers. Also in Japan, more than 1,000,000 tons per year of ORIMULSION is consumed as a fuel for power generation by a boiler, and ORIMULSION is regarded as being able to compete with all other fossil fuels for both price and supply in the long term.
ORINOCO BITUMEN contains 400 to 500 ppm of vanadium which is causative of high temperature corrosion due to vanadium attack an a boiler tube during combustion in a boiler. This unfavorable phenomenon can be suppressed by the addition of a magnesium salt. For this reason, the magnesium salt is added to ORIMULSION, and ORIMULSION having a standard composition given in Table 1 is currently shipped.
TABLE 1 ______________________________________ Anal- Analytical ytical Item value Unit Item value Unit ______________________________________ Specific gravity 1.01 /15.degree. C. Nitrogen content 0.4 wt % Water content 30 wt % Sulfur content 2.7 wt % Ash content 0.3 wt % Mg 500 ppm Total calorific 7000 cal/g V 250 ppm value True calorific 6400 cal/g Na 50 ppm value ______________________________________
In Table 1, the analytical values for Mg, V, and Na are those determined by elementary analysis.
ORINOCO BITUMEN have properties favorably comparable to fuel oil C and, hence, can be utilized as a fuel for a low speed diesel engine for ships, a diesel engine for power generation and the like. Properties of ORIMULSION and ORINOCO BITUMEN as a fuel age given, based on published materials, in Table 2 in comparison with properties of fuel oil C.
TABLE 2 ______________________________________ ORINOCO BITUMEN FUEL OIL C UNIT ______________________________________ SPECIFIC GRAVITY 0.976 0.889 80.degree. C./4.degree. C. VISCOSITY 1,528 34.8 cSt/80.degree. C. NITROGEN 0.63 0.22 % CONTENT SULFUR CONTENT 3.79 0.97 % WATER CONTENT &lt;0.1 &lt;0.1 % CALORIFIC VALUE About 10,000 10,000 Kcal/kg ASH CONTENT 0.13 0.01 % RESIDUAL CARBON 17.4 8.0 % V 400.about.500 Not more than 50 ppm Na 60.about.100 -- ppm ______________________________________
The use of ORIMULSION as the fuel for diesel engines poses a problem that the combustion of ORINOCO BITUMEN results in precipitation of the above magnesium salt which is then incorporated into a lubricating oil, causing abrasion of a cylinder wall.
Therefore, when the use of ORINOCO BITUMEN as a fuel for diesel engines is contemplated, ORIMULSION should be reprocessed to remove the magnesium salt, added as a measure for vanadium attack, and water added for improving handleability such as in transportation.
In utilizing conventional tarry materials or heavy fuel oils, such as asphalt, coal tar pitch, and bitumen, on a commercial scale, the removal of the above contaminants in addition to the removal of impurities is necessary. For this purpose, various means have hitherto been proposed in the art.
For example, Japanese patent application Kokai publication No. 7-34072 discloses a method wherein an acidic water having pH 2.5 to 6.5 is added to a heavy fuel oil in a high shear kneading device, such as a kneader, and they are kneaded under high shear force in such a state that the heavy fuel oil strings, thereby permitting metals, oxides, nitrogen components in the heavy fuel oil to migrate into the acidic water to remove them. In this publication, there is a working example using ORIMULSION.
Japanese patent application Kokai publication No. 60-106883 discloses a method for removing a salt contained in a heavy fuel oil. In this method, water is added to a mixed oil of a high-boiling hydrocarbon oil with a light oil added thereto, and a salt-containing water is separated and removed by means of a separator (for example, electric desalting tank).
Japanese patent application Kokai publication No. 55-12200 discloses a method wherein a heavy residual oil, asphaltene tar or the like is purified by extraction with a solvent, such as butyl alcohol/ketone, to promote phase separation, thereby promoting the removal of impurities.
Japanese patent publication No. 56-54036 discloses a method wherein a demulsifying agent is added to a salt-containing tar absorption oil produced in the step of purifying a coke oven gas, and the mixture is separated into an oil phase and a water phase containing a water-soluble salt, permitting the salt to be separated and removed from the absorption oil in a continuous and efficient manner.
In the methods disclosed in the above publications, however, water and an alkali metal or alkaline earth metal contained in an ultra-heavy fuel oil cannot be efficiently removed, and the agents added render these methods cost-ineffective, necessitating the establishment of a more effective removal method. In particular, the application of the above methods to ORIMULSION results in large power consumption for the operation of the kneader and the difficulty of handling a high viscosity tar. Thus, for the conventional methods, there is still room for improvement.